CONICET | Buscador de Institutos y Recursos Humanos

Vegetation associated to the main channel of the Paraná River is subjected to conditions imposed by flood and drought pulses. The objective of the presented work is to evaluate how the topographic variable, which indirectly determines the recurrence of floods, influences vegetation distribution on islands of a section of the lower Paraná River. Based on abundance-cover data on species for different flooding levels and applying classification and ordination multivariate techniques, six characteristic plant communities were identified and described: simple forests of marginal levees, mixed forests of internal levees, free-living (floating) lenitic community, aquatic rooted community, tall grass herbaceous community, and lower levee herbaceous community. Forests, both internal and marginal, are the most diverse and richest communities and, in spite of having similar topographic elevation, are distinguishable by their structure and species composition. In contrast, lowest richness and diversity values are found in the free-living lenitic community and in the lower levee herbaceous community, which are units that undergo highest flooding frequency. Results of the study indicate that the main variable affecting plant distribution is the topographic level, which affects the flooding recurrence and duration, but some communities, at the same topographic elevation, displays differences in spatial distribution and floristic composition. In some cases is due to their connectivity with the main watercourse. In other communities like forest, the differences seem not to be explained only by flooding.